We analyze whether affective polarization – the extent to which citizens feel sympathy towards partisan in-groups and antagonism towards partisan out-groups – can be aggravated by terrorism violence. Terrorist attacks intensify pre-existing ideological worldviews and partisan leanings and bring divisive political issues to the fore. Yet, they can also lead individuals from the entire political spectrum to come together and dissociate from the terrorists and their radical ideas. To identify causal effects, we exploit a series of natural experiments in Great Britain and leverage the timing of fatal far-right and Islamic terrorist attacks and the date of interview of respondents in the British Election Study. We find that Islamic attacks increase affective polarization whereas far-right attacks depolarize the electorate. We demonstrate that this discrepancy is largely driven by the salience of the attack – and the resulting threat perceptions – and the attitudes towards contentious and polarizing issues.